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NEW HERBICIDES FOR WARM-SEASON TURFGRASSES

Tim R. Murphy - Extension Weed Scientist

The University of Georgia

Several years ago, DMC (metsulfuron) and TFC (chlorsulfuron) were marketed for use in warm-season turfgrasses. DMC was sold by O. M. Scotts, and TFC was sold by Lesco. However, the active ingredients - metsulfuron and chlorsulfuron - were manufactured by DuPont. Sometime in 1995, DuPont made a decision to remove these herbicides from the turfgrass market. But there is good news, Riverdale Chemical Company has reintroduced these postemergence herbicides for use in warm-season turfgrasses. Metsulfuron will be sold under the trade name of Manor and chlorsulfuron will be sold under the trade name of Corsair.

Both metsulfuron and chlorsulfuron belong to the sulfonylurea herbicide family. Members of this family have extremely low toxicity to animals, but are highly phytotoxic to susceptible weeds at very low rates. For example, Manor, a 60 DF formulation, is labeled for use on Kentucky bluegrass, bermudagrass, centipedegrass, St. Augustinegrass and zoysiagrass at rates that range from 0.25 to 1.0 dry ounce of product per acre. At labeled rates warm-season turfgrasses and Kentucky bluegrass have excellent tolerance to metsulfuron. Chlorsulfuron is labeled for use in Kentucky bluegrass, bahiagrass and bermudagrass. While this herbicide can be applied on a broadcast basis, it primarily was used as a spot treatment to control clumpy tall fescue in labeled turfgrasses. Metsulfuron and chlorsulfuron inhibit the production of valine, leucine and isoleucine. These amino acids are used by plants to make proteins of which many serve as enzymes that catalyze the various biochemical reactions in plants. When amino acid synthesis is prevented, key enzymes are not produced and the weed slowly dies over a period of 1 to 3 weeks.

Manor provides excellent postemergence control of Pensacola bahiagrass, ryegrass, wild garlic and onion, and numerous broadleaf weeds (Table 1). Unlike phenoxy/dicamba herbicides (numerous trade names) and imazaquin (Image), metsulfuron does not temporarily delay the spring transition of bermudagrass. Additionally, in overseeding situations, Manor may be used at low rates on bermudagrass putting greens, and at slightly higher rates on bermudagrass fairways to hasten the transition from ryegrass to bermudagrass.

While Manor and Corsair control a wide range of weed species, these herbicides do not control summer annual grasses such as crabgrass, goosegrass and sandbur. Other weeds not controlled by these herbicides include dallisgrass, vaseygrass, broomsedge, carpetweed, johnsongrass and yellow thistle. Thus similar to all other selective turfgrass herbicides, the use of Manor and Corsair should be dictated by the weed species composition of a labeled turfgrass species.

Manor is excellent herbicide for use on warm-season turfgrasses, particularly St. Augustinegrass. This turfgrass species has very low tolerance to 2,4-D/dicamba containing herbicides which has greatly compounded the difficulty of controlling broadleaf weeds. However, St. Augustinegrass has excellent tolerance to Manor, and Manor controls numerous problem broadleaf weed species.

Both Manor and Corsair will be sold in the spring of 2000. Check with your turfgrass herbicide dealer or contact Riverdale Chemical Company at 1-800-345-3330 or at www.riverdalecc.com for additional information.

Table 1. Estimates of Weed Control with Metsulfuron (Manor)1

Common Name Scientific Name % Control with metsulfuron
bahiagrass Paspalum notatum 70-80%
barley, little Hordeum pusillum 10-20%
bedstraw, Catchweed Galium aparine 30-50%
bitterweed Helenium amarum 80-90%
broomsedge Andropogon virginicus 0%
burweed, lawn Soliva pterosperma 90-100%
buttercup Ranunculus spp. 90-100%
buttonweed, Virginia Diodia virginiana 50-70%
cancerweed Salvia lyrata 90-100%
carpetweed Mollugo verticillata 0%
carrot, wild Daucus carota 90-100%
catsear, dandelion Hypochaeris radicata 90-100%
chervil, wild Anthriscus sylvestris 90%
chickweed, common Stellaria media 90-100%
chickweed, sticky Cerastium glomeratum 90-100%
clover, white Trifolium repens 90-100%
copperleaf, hophornbeam Acalypha ostryifolia 75%
coreopsis, tickseed Coreopsis lanceolata 30-40%
corn salad Valerinella locusta 40-60%
curly dock Rumex crispus 90-100%
dandelion Taraxacum officinale 90-100%
dayflower, spreading Commelina diffusa 50-70%
dogfennel Eupatorium capillifolium 60-70%
doveweed Murdannia nudiflora 50-70%
fescue, tall Festuca arundinacea 20-30%
field madder Sherardia arvensis 30-40%
fireweed Erechtites hieracifolia 70- 80%
foxtail, knotroot Setaria geniculata 0%
garlic, wild Allium vineale 90-100%
geranium, Carolina Geranium carolinianum 50-60%
henbit Lamium amplexicaule 80-90%
hop clover Trifolium 50-70%
horsenettle Solanum carolinianum 30-40%
Johnsongrass Sorghum halepense 0%
lespedeza, annual Lespedeza striata 90-100%
marestail Conyza Canadensis 80-90%
morningglory, pitted Ipomoea lacunosae 60%
mullein Verbascum thapsus 80-90%
musk thistle Cirsium 60-70%
mustard, wild Brassica 60-70%
pennywort Hydrocotyle verticillata 80-90%
pigweed Amaranthus 80-90%
plains coreopsis Coreopsis tinctoria 90-100%
plantain, blackseed Plantago rugelii 90-100%
plantain, buckhorn Plantago lanceolata 90%
poorjoe Diodia teres 70-80%
purslane, common Portulaca oleracea 60-70%
Ragweed, common Ambrosia artemesifollia 30%
ragweed, giant Ambrosia trifida 75%
ragweed, lanceleaf Ambrosia bidentata 20-30%
ragwort or groundsel Senecio obovatus, S. glabellus 90-100%
red sorrel Rumex acetosella 70-80%
ryegrass Lolium multiflorum 40-60%
sesbania, hemp Sesbania exaltata 90%
sida, prickly Sida spinosa 90%
smartweed, Pennsylvania Polygonum pennsylvanicum 70 to 80%
sowthistle Sonchus asper 70-90%
speedwell, corn Veronica arvensis 90-100%
spurge, prostrate Euphorbia supina 90-100%
thistle, yellow Cirsium horridulum 20-30%
vetch, common Vicia sativa 90%
woodsorrel Oxalis 70-90%
yarrow Achillea millefolium 70-90%


1Compiled by John Boyd, Univ. of Arkansas,;Jim Taylor, Mississippi State Univ.; Tim Murphy, Univ. of Georgia; Fred Yelverton, North Carolina State Univ.; and Bert McCarty, Clemson Univ.